Your speaker needs repair. You'll probably find that a wire has separated from the panel (glue melted or failed) and that is what is causing the buzzing sound. If you or your prospective buyer are handy, the repair CAN be DIY. Magnepan sells the glue and the instructions to do it.
Otherwise you can ship it to them and they'll fix it. Turnaround time seems to be about 6-8 weeks.
Otherwise you can ship it to them and they'll fix it. Turnaround time seems to be about 6-8 weeks.